It is desirable for electrical and electronic devices to communicate and share information. A need has existed, e.g., for electronic communications between and among products such as data terminals, remote printers, personal computers, entertainment systems, refrigerators, washers, dryers, lights, and security and temperature control systems, all of which may be located within a single facility. Various schemes have been proposed to facilitate such inter-device communications, including radio transmission, light transmission and dedicated communications networks. It has been suggested in the past that such communications can be efficiently accomplished utilizing in situ power distribution networks. For example, U.S. Pat. No. 4,697,166 to Warnagiris et al. describes the ANI PLC (Power Line Carrier) system for inter-element communications.
As recognized in U.S. Pat. No. 5,471,190 to Zimmermann, there has been a growing interest in communications networks for home automation systems and products to facilitate the interconnection of lights, appliances, sensors and control devices. One system, critically described in the Zimmermann patent, was the so-called X-10 system. Eventually, an industry standard known as CEBus (Consumer Electronics Bus) was adopted by the Electronics Industries Association (EIA). The CEBus protocol (EIA IS-60) relates to a local area network that uses multiple media, including power line, radio, twisted pair, coaxial cable, and infrared signaling. The current CEBus protocol is designed to provide reliable communications within a single residence over one or more physical media.
The CEBus protocol provides for signal routers and brouters to interface between media; however, it does not provide for a repeater function when signals are unable to propagate successfully from point to point on an individual communications medium. This is a problem since communications media are not always sufficiently reliable to complete every desired point to point communication. Moreover, there are applications in which it is desirable to communicate not only within one residence but also between two or more residences. For communications between two different residences, point to point reliability is drastically reduced from that of the standard single residence scenario. Signal attenuation and noise may both contribute to this lack of reliability. This may be aggravated by distances or by the nature of the media. One example is an application that requires communication beyond a single family residence, e.g., between two residences or between one residence and a communicating device located outside the residence. Another example is the case where the communicating device is powered from three-phase service and communications are required across different phases of the power line. In commercial, industrial or multi-residence applications, point to point reliability is drastically reduced from that of the single residence scenario.
A goal of the present invention is to provide a reliable, low cost communications module that is adaptable, or configurable, for use in a number of modes in accordance with its location in a CEBus or similar network. The presently desired modes of operation include a source/interface mode in which the module serves as an interface between a host application and the network, a repeater mode in which the module receives and re-transmits message packets originated by another device and intended for a destination device, and a standalone device mode in which the module serves as a destination device for receiving messages from other devices (although the destination device mode may include the ability to originate messages or perform other application-based functions).